1. Field of the Invention
The present invention relates to a method and a communication module system having an interface module for interconnection with a communication module for linking a communication connection, e.g., a bus, to a user assigned to the communication module.
2. Description of Related Art
The interconnecting of control units, sensor systems, and actuator systems with the aid of a communication system including a communication connection, e.g., a bus, and corresponding communication modules has drastically increased in recent years in the construction of modern motor vehicles and in mechanical engineering, in particular in the machine tool field, and also in automation. Synergy effects through distribution of functions to multiple users, in particular control units, may be achieved in this case. These are referred to as distributed systems. Such distributed systems or networks thus include users as well as the bus system or multiple connecting bus systems connecting these users. The communication between different stations or users thus occurs more and more often via such a communication system or bus system, via which the data to be transmitted is transmitted in messages. This communication traffic on the bus system, access and receiving mechanisms, as well as error handling are regulated via a corresponding protocol.
For example, the CAN (controller area network) is established as a protocol in the automotive field. This is an event-controlled protocol, i.e., protocol activities such as the transmission of a message are initiated by events which have their origin outside the communication system. Unique access to the communication system or bus system is resolved via a priority-based bit arbitration. A condition for this purpose is that the data to be transmitted and thus each message is assigned a priority. The CAN protocol is very flexible; adding further users and messages is thus possible without problems as long as there are still free priorities (message identifiers). The aggregate of all messages to be transmitted in the network with priorities and their transmitting and/or receiving users and/or the corresponding communication modules is stored in a list, the communication matrix.
An alternative approach to event-controlled, spontaneous communication is the purely time-controlled approach. All communication activities on the bus are strictly periodic. Protocol activities such as the transmission of a message are only triggered by the elapse of a time which is valid for the entire bus system. The access to this medium is based on the distribution of time slots in which a transmitter has exclusive transmission right. The message sequence is typically to be established even before starting operation. Thus, a schedule is generated, which fulfills the requirements of the messages in regard to repetition rate, redundancy, deadlines, etc. This is referred to as the bus schedule. TTP/C is such a bus system, for example.
The advantages of both types of buses cited are combined in the approach of the time-controlled CAN, the TTCAN (time triggered controller area network). This fulfills the requirements described above for time-controlled communication and the requirements for a certain degree of flexibility.
TTCAN fulfills this by establishing communication rounds in exclusive time windows for periodic messages of specific communication users and arbitrating time windows for spontaneous messages to multiple communication users. TTCAN is based essentially on a time-controlled periodic communication, which is clocked by a user or communication module providing a master time, known as the time master, with the aid of a time reference message.
A further possibility for connecting different types of transmission is offered by the FlexRay protocol, which describes a rapid, deterministic, and error-tolerant bus system for use in a motor vehicle in particular. This protocol operates according to the method of time division multiple access (TDMA), the users or the messages to be transmitted being assigned fixed time slots in which they have an exclusive access to the communication connection, i.e., the bus. The time slots repeat in an established cycle, so that the instant at which a message is transmitted via the bus may be predicted exactly and bus access occurs deterministically. In order to optimally exploit the bandwidth for message transmission on the bus system, the cycle is divided into a static part and a dynamic part. The fixed time slots are located in the static part at the beginning of the bus cycle. In the dynamic part, the time slots are allocated dynamically. Exclusive bus access is only made possible therein for a short time in each case, a minislot.
As described above, there are multiple different transmission technologies and therefore multiple types of bus systems. Frequently, multiple bus systems of identical or different types must be connected to one another. A bus interface unit, a gateway, is used for this purpose. A gateway is thus an interface between different buses which may be of identical or different types, the gateway relaying messages from one bus to one or more other buses. Known gateways include multiple independent communication modules, the exchange of messages occurring via the processor interface (CPU interface) of the particular user and/or the corresponding interface module of the particular communication module. This data exchange, in addition to the messages transmitted by the user itself, places a high load on this CPU interface which, together with the transmission structure resulting therefrom, results in a relatively low data transmission rate. Furthermore, there are integrated communication controllers or communication modules which share a joint message memory and thus compensate for the structural disadvantages. However, such integrated communication modules are therefore very inflexible in regard to data transmission and are defined in particular for a specific number of bus connections. It has thus been shown that the related art is not capable of providing optimum results in every respect.
It is an object of the present invention to provide a communication module system and a special interface module, as well as a method, using which the exchange of data and/or messages, e.g., the generation of new data and/or messages, may be improved.